Stacking more images at Midwest Saltwater

[gparr]

Made another trip to Midwest Saltwater recently to practice my image-stacking photography. Getting a little better. Here are some shots.
Gary

Stack of 16 images

Stack of 12 images

Stack of 6 images

Stack of 8 images

Stack of 7 images

 

[Saltysteele]

Very nice, Gary! You ever get up to MI, you need to let us know! I'm sure a few of us would love to pick your brain!

Don! (dcmartinpc) you're putting in a good sized tank, getting some killer stuff from smokin' reefs, AND are down there in Niles.....

i'm thinking a couple sasparillas, and........ :snicker:


anyway, what does stacking a photo mean, Gary?

 

[Poseidon]

Those are excellent! I imagine the DOF is limitless with stacking, but how does it compare to a image shot at f22, 32, 45 etc?

 

[gparr]

Thanks, Salty. My dad lives in Davison (I was born in Flint and grew up in Clio), and I've already warned him that I was going to visit soon, but that he'd basically be serving as a hotel so I can meet you folks and fill up some digital cards.

Image stacking is a means of artificially increasing the depth of field so that more of the subject is in focus than is possible with a single shot. For example, in that first shot, if I used an aperture of f/25 to get maximum depth of field (the amount of the coral piece that is in focus front to back), I would have to make a decision about what part I wanted to go out of focus, because f/25, as close as I am to the coral, will not render the entire piece of coral in focus. (f/25 is the smallest aperture I can comfortably use with my 180 macro lens.) Typically I would choose to let the back portion go out of focus.

By stacking images, I can take a series of shots (16 in this case), starting by focusing at the front of the coral and moving the point at which I focus deeper into the scene with each successive shot. This technique also allows me to use a wider aperture (f/13 in this case), which keeps the area behind the coral blurred.

Once the images have been shot, you use software (I use Helicon Focus) to stack those images, eliminate what's out of focus, and keep what's in focus from each image.

Each image has to be exactly the same, i.e., you can't change the exposure, angle of view, or camera positioning. The only thing you change with each image is the point in the scene at which you focus. You also have to make sure you overlap your DOF with each shot so you don't have small lines of out of focus data.

It sounds much more complicated than it is, but I'll also say it has taken a little practice to get acceptable images. The quality isn't where I want it, but it's getting better.

Gary

 

[gparr]

Those are excellent! I imagine the DOF is limitless with stacking, but how does it compare to a image shot at f22, 32, 45 etc?

I haven't done a direct comparison, but haven't seen any degradation in the images. If I'm losing any quality from the stacking process, it's likely being offset by the fact that I can use a wider aperture and, thus, start with sharper individual images. In these shots, the smallest aperture I could use would have been f/25 or f/28. The smallest aperture on my 180 is f/32, and I don't want to use that if I don't have to. I had to use the 180 to reach into the aquarium and fill the frame with the coral piece. Any shorter lens would have required considerable cropping, which I try to avoid.
Gary